The purpose of this project is to study the mechanism by which guinea pig macrophage migration imhibitory factor (MIF) affects it target cell. This includes the following objectives: 1. The study of the effect of MIF on the metabolism of cyclic adenosine monophosphate (cyclic AMP) in macrophages. 2. To study the involvement of microtubules in the action mechanism of MIF. 3. Characterize the specific macrophage receptor for MIF. 4. To examine the effect of MIF on specific macrophage membrane functions. 5. To use knowledge gained from above for development of drugs able to block cell mediated immune reactions in vivo. BIBLIOGRAPHIC REFERENCES: Pick, E., Modulation of lymphokine generation and effector function by drugs, In: "7th International course on transplantation and clinical immunology", J.L. Touraine, ed., pp. 71-78, Simep, Lyon, 1976 (in press). Pick, E., Lymphokines - physiological control and pharmacological modulation of their production and action. In "Immunopharmacology", J.W. Hadden F. Spreafico and S. Garattini, ed., Plenum Press, New York, 1976 (in press).